The colour orange occurs between red and yellow in the visible spectrum at a wavelength of about 585–620 nm, and has a hue of 30° in HSV colour space. It is numerically halfway between red and yellow in a gamma-compressed RGB colour space, the expression of which is the RGB colour wheel. The complementary colour of orange is azure. Orange pigments are largely in the ochre or cadmium families, and absorb mostly blue light

The orange is a very well known fruit and is considered a valuable medicinal herb as well. Initially the orange probably originated from China. However, by the Middle Ages the fruit was a favorite in many lands and its herbal qualities were highly regarded by Arabian physicians in the Middle East. Oil extracted from the flowers was discovered and prepared as a scent during the 16th century, supposedly by an Italian princess named Anna-Marie de Nerola; she used the oil to scent her gloves. For this reason, the neroli floral oil, as it is now known is prohibitively expensive and famous as a perfume. The use of medicinal oranges is the main domain of the Chinese herbalists, who are still the greatest enthusiasts of medicinal oranges and its remedies today. Medicinal preparations are mainly made from the bitter Seville orange - C. aurantium or the sweeter tangerines and satsumas - C. reticulata. The bitter orange remedies have a great repute in many places.

Function:1. Anti-oxidation, reduce the damage of envoronmental pollution on the body;2. Consolidate the connective tissue, strengthen the skin, bones, teeth and muscle;3. Promote collagen synthesis, help wound healing;4. Involved in cholesterol metabolism and help lipoclasis;5. Promote the absorption of iron and calcium, prevent scurvy.